Expression of An Antisense Brassica oleracea GIGANTEA (BoGI) Gene in Transgenic Broccoli Causes Delayed Flowering, Leaf Senescence, and Post-Harvest Yellowing Retardation

Abstract

Broccoli (Brassica oleracea L. var. italica) is an important vegetable crop all over the world. However, rapid post-harvest senescence in harvested floral heads reduces its value. Mutation in GIGANTEA (GI) caused delay of flowering and increased tolerance level to H2O2-induced oxidative stress in Arabidopsis. BoGI, a GI orthologue, was isolated and characterized from B. oleracea. BoGI mRNA is expressed throughout development and can be detected in leaves, stem, root, and flowers. Further analysis indicated that the expression of BoGI is modulated by the circadian clock. To investigate the senescence flowering-associated mechanism regulated by BoGI gene and the agricultural application of BoGI in controlling flowering time and floret yellowing for B. oleracea, constructs containing antisense cDNA of BoGI driven by 35S or a flower-specific AP1 promoter were transformed into B. oleracea and the transgenic plants were generated. The flowering time and the senescence of the detached leaves were significantly delayed in transgenic 35S::BoGI antisense plants. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis showed that clear reduction of BoGI expression was observed in these 35S::BoGI antisense plants compared to that in wild-type plants. Furthermore, post-harvest yellow and flower senescence was delayed in AP1::BoGI antisense plants. These findings indicate that BoGI could be involved in regulation of flowering time, leaf, floret, and flower senescence in broccoli.